Median refers to the value which lies in the middle of the data (when arranged in an increasing or decreasing order).
Arranging the data in ascending order: 50, 60, 70, 80, 90, 100, 110, 120
Since no. of observations is 8, an even number, there will be two middle terms. So, the median will be the average of (82)th and the (82+1)th terms.
Median will be the average of the 4th and 5th terms
So, median = 80+902 = 85.